Process for bonding hydraulic cementitious materials



United States Patent PROCESS FOR BONDING HYDRAULIC CEMENTITIOUSMATERIALS Herbert J. Larsen, deceased, late of Washington, D. C., byPhyllis H. Larsen, administratrix, Washington, D. C., and George G.Groome, Takoma Park, Md, assignors, by mesne assignments, to saidPhyllis H. Larsen, Washington, D. C.

No Drawing. Application April 14, 1954, Serial No. 423,236

8 Claims. (Cl. 117-70) This invention relates to a process for bondinghydraulic cementitious materials to base materials and moreparticularly, to a method of plastering whereby cementitious materialssuch as Portland cement or gypsum plaster may be firmly bonded to anybase structure such as, for example, concrete block, cinder block, wood,brick, rock lath, and monolithic concrete slabs. The invention isfurther directed to the laminated structure resulting from the use ofthe method of plastering described herein.

The problem of applying hydraulic cementitious materials as a surfacingagent to wood, cinder block, monolithic concrete and the like is adifiicult one, and none of the solutions hitherto suggested have beenentirely satisfactory. It is well known, for example, that one cannotsuccessfully apply a coating or layer of a finishing coat of cement to aset concrete base because the finishing coat cracks and does not form afirm, permanent bond between the concrete base and the applied coating.Nor is it possible to apply coatings or layers of such cementitiousmaterials to other kinds of base materials, such as wood, metal, glassand the like. In fact, much of the new building in this country iscomposed of poured, smooth monolithic slab concrete and no practical wayis now available for applying plaster finish coats to such materials.Consequently, most of the finish coats for wall surfaces and the likeare painting jobs, and the rough cast flooring has been surfaced withasphalt tile for appearance.

Thus, the problem of developing a process for surfacing base structuralmaterials of the kind stated with plasters such as lime-gypsummaterials, fine finish coatings of Portland cement, and the like, is avery real one in this art. The method most commonly used heretofore isthat of applying an adhesive coating to the base material which coatingis in the nature of an asphalt emulsion. Over this adhesive coating isapplied the plaster. It is necessary to apply the plaster immediatelyafter application of the adhesive coating since the action depends uponthe tack qualities of the adhesive. In the coarse of time such finishcoatings applied according to that process crack and craze because ofthe deterioration of the underlying film of asphalt, a materialnotoriously susceptible to oxidation, temperature changes, and internalbreak-down of the constituents thereof.

The present invention is directed to the method of applying plasterwhereby the plaster is interlocked with the base material through theintermediary of the bonding agent. It can be readily seen that by virtueof this interlocking effect obtained according to the method hereindisclosed results are possible which were not realized by prior artprocesses wherein the plaster was, in effect, glued to the basematerial.

The presently described process contemplates the use of a novel bondingagent described and claimed in applicants co-pending application, SerialNo. 281,914, filed April 11, 1952, for Bonding Adhesives, Particularlyfor ice Bonding Hydraulic cementitious Materials, now abandoned. Thisbonding agent is an aqueous emulsion of the polyvinyl acetate resinswhich are compounded with additional agents to produce the bondingmaterial suitable for use in the presently described process.

One of the outstanding features of the present invention is the use of aspecial bonding agent which permits the plaster to be applied at anytime after the application of the bonding agent to the base materialeven if the bonding agent has dried out. In methods employed heretoforeit was essential to apply the plaster immediately after the applicationof the asphalt emulsion for, in the event that the asphalt dried, it wascompletely ineffectual in gluing the finish coat to the base material.

It has now been discovered that polyvinyl acetate emulsions haveremarkable properties for use as bonding agents in the practice of ourinvention. These emulsions do not oxidize as do the asphalt emulsions.Moreover, the deposited solids of these emulsions readily re-emulsifywhen brought into contact with water, as, for example, when wet gypsumplaster is applied to a base structure covered with such depositedsolids, essentially polyvinyl acetate.

While the invention embraces broadly the use of such polyvinyl acetateemulsions and, as such, is entirely operative, it has been found thatthe addition of plasticizers and the like is beneficial.

One bonding agent found suitable for use in the present invention is anemulsion of polyvinyl acetate resin with the addition of plasticizingagents including polychlorinated diphenyl, tricresyl phosphate, andhexylene glycol.

One suitable composition is composed of about parts by weight of thecommercial polyvinyl acetate emulsion (55 to 60% solids) 8 parts byweight of the polychlorinated diphenyl (Arachlor), 8 parts by Weight oftricresyl phosphate, and 2 parts by Weight of hexylene glycol dissolvedin 5 parts by weight of water. in formulating this mixture, it ispreferred to first admix the polychlorinated diphenyl and tricresylphosphate together at a slightly raised temperature, about 100-110" F.to blend these two materials thoroughly together after which the mixtureis added to the polyvinyl acetate emulsion with stirring. Thereafter thehexylene glycol, admixed with the amount of water stated above isstirred into the aqueous emulsion and the entire mixture agitated forabout an hour at fairly low speeds, of the order of 400 R. P. M. Toorapid agitation may result in a breakdown of the emulsion at this stage.The agitation, of course, depends upon such factors as the type ofagitator used, and quantities being blended together. The agitation issimply for the purpose of rendering the mixture homogeneous.

Variations can be made in the amounts of ingredients stated above. Ithas been found that for best results the polychlorinated diphenyl andtricresyl phosphate should be used in about equal amounts and these canvary from about 4 to 12 parts by weight of each to 108 parts by weightof the base polyvinyl acetate emulsion. Less than 4 parts by weight ofeach tends to render the deposited and dried films somewhat brittle, andmore than about 12 parts by weight tends to make the films a bit toosoft so that cold flow could occasionally occur.

The method of applying plaster according to the present invention is asfollows: The base material which may be any of the building materialspresently used need not be prepared in any way and may, in fact, beeither damp or dry when the bonding agent is applied. The bonding agentis then sprayed or brushed over the base surface to be covered and formsa film thereon. The hydraulic cementitious material, such as Portlandcement or gypsum plaster, is then applied over the film. The plasteringmay material.

be delayed for any desired length of time after applying the film ofbonding agent. This is due to the fact that a film of bonding agentitself is redispersible and will reemulsify after having dried out. Asthe laminated structure dries it is possible that crystals of gypsum inthe plaster fall in the emulsion of the bonding agent and the plasticparticles in the bonding agent draw together until a barrier is formed.Similarly, the particles in the emulsion of the bonding agent fill thepores in the base Thus, it can be seen that an interlocking is obtainedbetween the finish coat and the base which effect is not contemplated byany of the prior art methods.

However, while it is believed the enhanced adhesiveness is due to thisinterlocking of plaster and emulsion film, the invention is not tobelimited to this theory. As stated above, the bonding agent may consistsimply of the commercially available polyvinyl acetate emulsions.Advantageously, however, plasticizers such as those referred to aboveare also present.

While the utility of this invention in bonding base structural materialssuch as concrete slabs, wood, and steel to finish coatings of hydrauliccementitious materials has been emphasized, it is obvious that thepresently described process is applicable in other fields as well, forexample, in bonding wood to wood.

What is claimed is:

l. A laminated structure comprising a base material, a coating thereoncomprising a film composed of the solids deposited from an aqueousemulsion of a polyvinyl acetate, said solids being re-emulsifiable, anda set hydraulic cementitious material overlying and adhering to saidcoatmg.

2. An adhesive composition comprising about 100 parts by weight of anaqueous emulsion of a polyvinyl acetate resin, about 4 to 12 parts byweight of a polychlorinated diphenyl, about 4- to 12 parts by weight oftricresyl phosphate and about 2 parts by weight of hexylene glycol, saidcomposition, when applied as a coating and allowed to dry, yielding awater permeable film.

3. An adhesive composition comprising about 100 parts by weight of anaqueous emulsion of a polyvinyl acetate resin, about 8 parts by weightof a polychlorinated diphenyl, about 8 parts by weight of tricresylphosphate, and about 2 parts by weight of hexylene glycol, saidcomposition, when applied as a coating and allowed to dry, yielding awater permeable film.

4. The process of applying a hydraulic cementitious material whichcomprises coating a base material with a film of aqueous emulsion ofresin the deposited solids of which will re-emulsify in contact withwater, the aqueous 4 emulsion of resin comprising about parts by weightof an aqueous emulsion of a polyvinyl acetate resin, about 8 parts byweight of a polychlorinated diphenyl, about 8 parts by weight oftricresyl phosphate, and about 2 parts by weight of hexylene glycol,drying the film, and re-emulsifying the fihn by applying an aqueousmixture of hydraulic cementitious material thereto.

5. The process of applying a hydraulic cementitious material whichcomprises coating 21 base material with a film of an aqueous emulsion ofpolyvinyl acetate the deposited solids of which will re-emulsify incontact with water, drying the film, and thereafter re-emulsifying thepolyvinyl-acetate film by applying an aqueous mixture of hydrauliccementitious 'material'th'ereto.

6. In a process for applying a hydraulic cementitious material to a basematerial comprising the steps of coating the base material with a filmcomposed essentially of an aqueous emulsion of polyvinyl acetate, thedeposited solids of which will re-emulsify in contact with water, dryingthe film, and thereafter re-emulsifying the polyvinyl acetate film byapplying the hydraulic cementitious material.

7. The process of applying a hydraulic cementitious material comprisingcoating a base material with a film of an aqueous emulsion of polyvinylacetate and hexylene glycol the deposited solids of which willre-emulsify in contact with water, permitting the film to dry, andthereafter re-emulsifying the polyvinyl acetate film by applying anaqueous mixture of hydraulic cementitious material thereto.

8. The process of applying a hydraulic cementitious material whichcomprises coating a base material with a film of an aqueous emulsion ofpolyvinyl acetate, hexylene glycol and tricresyl phosphate, thedeposited solids of which will re-emulsify in contact with water, dryingthe film, re-emulsifying the polyvinyl acetate film by applying anaqueous mixture of hydraulic cementitious material thereto.

References Cited in the file of this patent UNITED STATES PATENTS GreatBritain July 12, 1940

5. THE PROCESS OF APPLYING A HYDRAULIC CEMENTITIOUS MATERIAL WHICHCOMPRISES COATING A BASE MATERIAL WITH A FILM OF AN AQUEOUS EMULSION OFPOLYVINYL ACETATE THE DEPOSITED SOLIDS OF WHICH WILL RE-EMULSIFY INCONTACT WITH WATER, DRYING THE FILM, AND THE THEREAFTER RE-EMULSIFYINGTHE POLYVINYL-ACETATE FILM BY APPLYING AN AQUEOUS MIXTURE OF HYDRAULICCEMENTITIOUS MATERIAL THERETO.